Potassamide induced in situ benzylation of 5, 6-dihydroisoquinolines: structure of novel products

Abstract

Potassamide induced in situ benzylation of 1-alkyl-4-cyano-3-methoxy-5,6-dihydroisoquinolines (1a-b) with benzyl iodide gave the 5-benzyl-, 5,9-dibenzyl- and 4,4-dibenzyl-5,6-dihydroisoquinolines (9a-b, 8a-b & 10a-b), isoquinoline derivatives (4a-b) and diastereomeric mixture of 4-benzyl-1,2,3,4-tetrahydroisoquinolin-3(2H)-ones (11a-b & 11'a-b). Structures were assigned on the basis of spectral data [Mass, ¹H & ¹³C NMR, 2D NOESY]. A few reactions carried out to transform the diastereomeric mixture of compounds 11a & 11'a to the spirobenzylisoquinoline system 7a isomeric with naturally occurring ochotensane system 6a are discussed.